In eukaryotic cells, polyunsaturated fatty acids are oxygenated by three general systems: 1) cyclooxygenases (COXs) and related fatty acid oxygenases, including pathogen-inducible oxygenases (PIOXs) identified in plants, animals and bacteria; 2) lipoxygenases; and 3) cytochrome P-450. Presently there are 2 COX isozymes known, COX-1 and COX-2. The predicted amino acid sequences of COX-1 cloned in chicken and mammals possesses approximately 60% amino acid sequence identity with COX-2.
The cyclooxygenation of arachidonic acid, catalyzed by two forms of cyclooxygenase produces prostaglandins which, in turn, regulate neurotransmission and immune and inflammatory responses by activating receptors coupled to cAMP formation. (Goetzl et al., FASEB J., 9:1051, 1995). For example, inflammation is both initiated and maintained, at least in part, by the overproduction of prostaglandins in injured cells. The central role that prostaglandins play in inflammation is underscored by the fact that those aspirin-like non-steroidal anti-inflammatory drugs (NSAIDS) that are most effective in the therapy of many pathological inflammatory states all act by inhibiting prostaglandin synthesis. NSAIDs are analgesic/antiinflammatory/antipyretic medications that act as inhibitors of the cyclooxygenase active site of COX isozymes. Important mechanistic differences in the actions of individual NSAIDs with the COX active site exist. Of the NSAIDs in medical use, only aspirin is a covalent modifier of COX-1 and COX-2.
There is increasing emphasis on the development of compounds that modulate cyclooxygenase activity and methods for identifying such compounds. Therefore, there is a need for improved methods to study the effectiveness of existing anti-inflammatory drugs and to evaluate the effectiveness of potential anti-inflammatory agents, at the molecular level, as well as for reagents for use in such methods.